I can’t help it, I keep ‘em. I even have an old Criminology textbook from Community College.

I sold the textbooks, but not the novels or poetry anthologies from my lit electives.

I keep them. If I don’t get a chance to read the whole thing while I’m taking a certain class, I figure I’ll read all of them back to back, someday.

I kept them to use as reference items in future classes.

I keep some, I sell others. The ones concerning topics I’m most interested in, I keep. I’ve kept all my linguistics textbooks, for example. But there are others that I get rid of. I don’t want to be like my dad. He kept every textbook and they just take up space!

I keep the ones I think I’ll use later. It’s always nice to have a reference text written at a lower level when you’re studying more advanced material.

I still have every book I’ve purchased since Fall of ‘07 for school.
Some of which, I keep due to my interest in the subject and my expectation of needing it in the future. e.g. my big “Maintaining and repairing PCs” book.
There are others that I don’t foresee ever reading again, but I don’t want to deal with the school bookstore, nor do I want to deal with packing it all up and shipping it off. Its much less stressful for me to let them gather dust.

Sometimes, I delude myself that I’m going to come back to them one day. Others, I see as just piles of change.

I couldn’t afford to buy most of my books in college. I used the textbooks on reserve in the library. The ones I did buy, I couldn’t afford not to sell back.

Since starting grad school, I have kept all of the books I have bought (or loaned them out, never to be returned…). I have used them for references in classes, but never for real work.

Anything in my field, anything that I think I might refer to again, and anything that I just plain found interesting I would keep, especially if I have marked and annotated it. I did sell back my math, science, and most of my social sciences books, but I kept everything in literature and philosophy and languages. Over the years I have referred to them many times.

I am also keeping the textbook for my recent film class, which is not only a great guide to understanding movies but also a checklist of films I’d like to see.

I have mine along with every note I took. They occasionally come in handy. If the bookstore didn’t pay 20% of what I paid I might have sold them.

I sold all of the college textbooks, but I kept some of my law school books.

I have kept almost all of my old textbooks, and I even kept a few of my wife’s textbooks that she didn’t want anymore. To be fair, a lot of them are still relevant now that I am in graduate school and will continue being relevant afterward. The others are just interesting.